Two-dimensional analysis of short-channel delta-doped GaAs MESFETs

Key design parameters for delta-doped GaAs MESFETs, such as delta doping profile, top layer background doping density, and scaling of lateral feature size, are investigated using a two-dimensional numerical simulation. A three-region (delta-doped conducting channel, top layer, and substrate) velocity-field relation is implemented in the model as appropriate for the particular device structure which is simulated. Simulation results show excellent agreement with a fabricated 0.5-μm gate-length delta-doped GaAs MESFETs based on atomic layer epitaxy material. An extrinsic transconductance of 370 mS/mm and a drain-source current of 270 mA/mm are obtained for typical devices, and the maximum transconductance is as high as 400 mS/mm. These are the best DC results yet reported for 0.5-μm gate-length delta-doped GaAs MESFETs. Considerations of design and optimization are discussed in terms of threshold voltage sensitivity, transconductance, current drive capability, and cutoff frequency, based on both simulation and experiment results